Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$217.59	4.466%	$227.3076	$227.31	$227.30	$227.30
Purchase #2	$93.40	10.351%	$103.0678	$103.07	$103.05	$103.10
Purchase #3	$52.84	12.572%	$59.483	$59.48	$59.50	$59.50
Purchase #4	$142.69	6.185%	$151.5154	$151.52	$151.50	$151.50
Purchase #5	$234.73	12.796%	$264.7661	$264.77	$264.75	$264.80
Purchase #6	$250.64	12.787%	$282.6893	$282.69	$282.70	$282.70
Purchase #7	$184.74	6.405%	$196.5726	$196.57	$196.55	$196.60
7 purchase totals =	$1,176.63		$1,285.4018	$1,285.41	$1,285.35	$1,285.50